Midfoot bone replacement

ABSTRACT

A method of implanting a midfoot replacement in an adult human foot comprising includes removing at least a portion of at least one midfoot bone from the adult human foot. The method also includes inserting a midfoot replacement into the adult human foot such that a proximal side of the midfoot replacement engages at least one of a calcaneus and a talus of the adult human foot, and a distal side of the midfoot replacement engages at least one of a first metatarsal and a fourth metatarsal of the adult human foot.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.17/986,994, filed Nov. 15, 2022, which is a continuation of U.S. patentapplication Ser. No. 16/779,244, filed Jan. 31, 2020, now U.S. Pat. No.11,497,613, which in turn claims the benefit of priority to U.S.Provisional Application No. 62/948,341, filed Dec. 16, 2019, thecontents of both of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This disclosure relates generally to surgical implants, and morespecifically to surgical implants for replacing midfoot bones of apatient.

BACKGROUND

Charcot neuropathic osteoarthropathy (CN), commonly referred to as theCharcot foot, is a condition causing weakening of the bones in the footthat can occur in people who have significant nerve damage (neuropathy).More particularly, Charcot foot is commonly found in diabetic patients,with between 1 and 5 percent of diabetic patients developing Charcotfoot, though this number may be higher due to Charcot foot frequentlygoing undiagnosed. The weakening of the midfoot bones causesdislocations and fractures in the midfoot bones. Left untreated, Charcotfoot can result in the foot developing a rocker-bottom shape, which cancause severe health complications and potentially require amputation ofthe foot.

Currently there are a number of solutions for fixating and fusing bonesof the midfoot to assist in bone healing and repair of Charcot foot.Some of these solutions attempt to repair midfoot bones by fixatingimplants or devices and bones to one another or to the calcaneus ortalus, or to fixate or fuse bones by means of external fixation.However, fixing the bones to one another or externally fixating thebones requires subsequent surgical interventions to add and/or removeadditional hardware, can cause patient emotional and physical decline,and require prolonged recovery periods. Moreover, such methods arereliant on the bone quality or sustainability of the structures of themidfoot, which may be compromised or deteriorate due to progression ofthe Charcot foot disease. In addition, conventional internal or externalfixation surgeries are very costly and may be avoided by patients due tothe cost, insurance and/or patient cost load, extensive procedure andrecovery time, liability concerns, and poor outcomes.

Another solution to Charcot foot is to attempt to fixate some of themidfoot bones to bones of the hindfoot or forefoot. However, fixatingbones to the hindfoot or forefoot still rely on the diseased bonesand/or joints to maintain sufficient bone quality for fixation, oftenrequire subsequent surgeries with prolonged recovery periods, and canalso be very costly for the patient, insurance provider, surgeons, andthe hospitals.

Moreover, the known surgical remedies for Charcot foot are oftenunsuccessful, and may result in irreparable damage to the midfoot regionand the adjacent bones, which requires amputation of the foot.Amputation, however, often results in the patient's health deterioratingdue to surgical complications or the inability of the patient to engagein physical activity after amputation of the foot, with studies showinga 73% 5-year mortality rate after diabetic foot amputation.

What is needed, therefore, is a device that can improve patientoutcomes, increase the stability of feet impacted by Charcot foot,reduce the number and length of surgical procedures to treat Charcotfoot, and reduce the cost of treating Charcot foot.

SUMMARY

In one embodiment, an implant for a human includes a body having asuperior surface, an inferior surface, a distal surface, and a proximalsurface. The proximal surface is configured to engage the talus and thecalcaneus of an adult human, and the distal surface configured to engageat least the first and fourth metatarsals of the adult human. The distalsurface has a largest distal height and a largest distal width that isgreater than the largest distal height, and the proximal surface has alargest proximal height and a largest proximal width that is greaterthan the largest proximal height.

In another embodiment, a method of implanting a midfoot replacement inan adult human foot comprising includes removing at least a portion ofat least one midfoot bone from the adult human foot. The method alsoincludes inserting a midfoot replacement having a body into the adulthuman foot such that a proximal side of the body engages at least one ofa calcaneus and a talus of the adult human foot, and a distal side ofthe body engages at least one of a first metatarsal and a fourthmetatarsal of the adult human foot.

In a further embodiment, a kit comprises a first implant for a humanmidfoot, which comprises a body having a superior surface, an inferiorsurface, a distal surface, and a proximal surface. The proximal surfaceis configured to connect to the talus and the calcaneus of an adulthuman, and the distal surface configured to connect to at least thefirst and fourth metatarsals of the adult human. The distal surface hasa largest distal height and a largest distal width that is greater thanthe largest distal height, and the proximal surface has a largestproximal height and a largest proximal width that is greater than thelargest proximal height. The kit further includes at least two fixatingfasteners configured to affix the body to the talus, calcaneus, and thefirst and fourth metatarsals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a superior-proximal perspective view of a midfoot implant.

FIG. 2 is a proximal plan view of the midfoot implant of FIG. 1 .

FIG. 3 is a distal plan view of the midfoot implant of FIG. 1 .

FIG. 4 is a medial side plan view of the midfoot implant of FIG. 1 .

FIG. 5 is a medial-proximal perspective view of the midfoot implant ofFIG. 1 .

FIG. 6 is a lateral side plan view of the midfoot implant of FIG. 1 .

FIG. 7 is a superior view of the midfoot implant of FIG. 1 .

FIG. 8 is a distal-inferior view of the midfoot implant of FIG. 1 .

FIG. 9 is a superior view of an adult human foot in which the midfootimplant of FIG. 1 is implanted.

FIG. 10 is a medial side plan view of the adult human foot of FIG. 9with the midfoot implant of FIG. 1 implanted.

FIG. 11 is a process diagram of surgically implanting a midfoot implantsuch as the midfoot implant of FIG. 1 .

FIG. 12 is a schematic illustration of a kit that includes the midfootimplant of FIG. 1 .

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theembodiments described herein, reference is now made to the drawings anddescriptions in the following written specification. No limitation tothe scope of the subject matter is intended by the references. Thisdisclosure also includes any alterations and modifications to theillustrated embodiments and includes further applications of theprinciples of the described embodiments as would normally occur to oneskilled in the art to which this document pertains.

The terms “comprising,” “including,” “having,” and the like, as usedwith respect to embodiments of the disclosure, are synonymous. As usedherein, the term “approximately” is to be interpreted to encompass therange that one of ordinary skill in the art would consider reasonable inthe context of the particular use of the term. Alternatively, the term“approximately” may be interpreted to include all values that are within±10% of the reference value.

FIG. 1 depicts a first embodiment of a midfoot implant 100 that replacesbones in the midfoot region of an adult human patient's foot so as tostabilize the patient's midfoot region. While the illustrated midfootimplant 100 is configured for implantation in a patient's left foot, thereader should appreciate that the midfoot implant can be mirrored aboutthe proximal-distal plane for use in a patient's right foot. The midfootimplant 100 is a solid body 104 formed of a rigid biocompatiblematerial. In one embodiment, the solid body 104 of the midfoot implant100 is formed of a rigid biocompatible polymer that may, for example, beformed by an additive process, such as three-dimensional printing, by acasting process, or by a subtractive process, such as milling. The solidbody 104 of the midfoot implant 100 has a proximal end surface 108, adistal end surface 112, a medial side surface 116, a lateral sidesurface 120, a superior surface 124, and an inferior surface 128.

In the illustrated embodiment, the solid body 104 is integrally formedas a single piece of material, for example as a monolithic body. Inother embodiments, the solid body 104 of the midfoot implant may beformed of two or more pieces of material. More particularly, theproximal end surface 108 and the distal end surface 112 may be ondifferent pieces of material.

As depicted in FIG. 2 , the proximal end surface 108 is defined by aconvex superior edge 140, a concave inferior edge 144, a medial edge148, and a lateral edge 152. In the illustrated embodiment, the proximalend surface 108 is substantially planar, though the reader shouldappreciate that in other embodiments the proximal end surface may beshaped so as to conform to the talus and calcaneus bones of thepatient's foot. More particularly, in some embodiments, the distal endsurface 112 may include one or more protuberances or indentations thatconform to one or more of the calcaneus and talus bones of the patient.In some embodiments, the proximal end surface 108 may be smooth, thoughin other embodiments, the proximal end surface 108 may have a roughenedlattice-like or web-like structure that is porous and rough.

The proximal end surface 108 has a largest width 154 measured from theoutermost part of the medial edge 148 to the outermost part of thelateral edge 152 and a largest height 156 measured from the uppermostpart of the convex upper edge 140 to the lowermost part of the concavelower edge 144. The largest width 154 is greater than the largest height156 or, in other words, the proximal end surface 108 is wider than it istall, so as to conform generally to the anatomical shape of the midfootregion of the patient's foot.

The proximal end surface 108 also defines the proximal ends of twothrough-holes 160, 164, one of which is on the medial side and the otherof which is on the lateral side of the proximal end surface 108. As willbe described in detail below, the medial through-hole 160 is extendsfrom the talus to the first metatarsal of a patient, while the lateralthrough-hole 164 extends from the calcaneus to the fourth metatarsal ofthe patient. The proximal end of the medial through-hole 160 istherefore arranged vertically in a middle third, more particularlyapproximately halfway, between the uppermost portion of the convexsuperior edge 140 and the lowermost portion of the concave inferior edge144, and spaced apart from the medial edge 148 by a distance of betweenapproximately 5% and approximately 20% of the largest width 154, and inone particular embodiment, approximately 12.5% of the largest width 154.The proximal end of the lateral through-hole 164 is arranged verticallyin the upper third of the proximal end surface 108, and spaced apartfrom the lateral edge 152 by a distance of between approximately 10% toapproximately 25% of the largest width 154, and in one particularembodiment, approximately 15% of the largest width 154.

FIG. 3 illustrates the distal end surface 112 of the midfoot implant100. The distal end surface 112 is defined by a convex superior edge180, a concave inferior edge 184, a medial edge 188, and a lateral edge192. Again, the distal end surface 112 of the illustrated embodiment issubstantially planar, though the reader should appreciate that in otherembodiments the distal end surface 112 may be shaped so as to conform toone or more of the metatarsals of the patient, and more particularly tothe first and fourth metatarsals. Additionally, in some embodiments, thedistal end surface 112 may include one or more protuberances orindentations that conform to one or more of the metatarsals of thepatient. In some embodiments, the distal end surface 112 may be smooth,though in other embodiments, the distal end surface 112 may have aroughened lattice-like or web-like structure that is porous and rough.

The distal end surface 112 has a largest width 194 measured from theoutermost portion of the medial edge 188 to the outermost portion of thelateral edge 192 and a largest height 196 measured from the uppermostpart of the convex superior edge 180 to the lowermost part of theconcave inferior edge 184. The largest width 194 is greater than thelargest height 196 or, in other words, the distal end surface 112 iswider than it is tall. Additionally, the largest width 194 and largestheight 196 of the distal end surface 112 are less than the respectivelargest width 154 and largest height 156 of the proximal end surface108. Thus, the midfoot implant 100 generally conforms to the anatomicalshape of a patient's midfoot region.

The distal end surface 112 defines the distal ends of the through-holes160, 164. In particular, the distal end of the medial through-hole 160is located vertically in a middle third, more particularly approximatelyhalfway, between the uppermost portion of the convex superior edge 180and the lowermost portion of the concave inferior edge 184, and isspaced apart from the medial edge 188 by a distance of betweenapproximately 15% and approximately 25% of the largest width 194 of thedistal end surface 112, and in one particular embodiment approximately20% of the largest width 194. The distal end of the lateral through-hole164 is also located vertically in a middle third, more particularlyapproximately halfway, between the uppermost portion of the convexsuperior edge 180 and the lowermost portion of the concave inferior edge184, and is spaced apart from the lateral edge 192 by a distance ofbetween approximately 15% and approximately 25% of the largest width 194of the distal end surface 112, and in one particular embodimentapproximately 20% of the largest width 194.

FIGS. 4 and 5 illustrate the medial side surface 116 of the midfootimplant 100. The medial side surface 116 is defined on the proximal endby the medial edge 148 of the proximal end surface 108 and on the distalend by the medial edge 188 of the distal end surface 112. On thesuperior and inferior sides, the medial side surface 116 blends smoothlyinto the respective superior surface 124 and inferior surface 128.

In some embodiments, a portion or the entirety of the medial sidesurface 116 may include a lattice-like or web-like outer structure 200that is porous and rough. In other embodiments, the entire medial sidesurface 116 may be smooth and solid.

The medial side surface 116 defines a medial side maximum length 204spanning from the furthest proximal portion of the medial edge 148 ofthe proximal end surface 108 to the furthest distal portion of themedial edge 188 of the distal end surface 112. The medial side maximumlength 204 may be, for example, between approximately 2 cm andapproximately 4 cm. In one particular embodiment, the medial sidemaximum length 204 may be approximately 2 cm shorter than the medialside length of an average adult human midfoot, or approximately 3 cm, toallow the midfoot implant 100 to be used in a variety of patients.

FIG. 6 illustrates the lateral side surface 120 of the midfoot implant100. The lateral side surface 120 is defined on the proximal end by thelateral edge 152 of the proximal end surface 108, and on the distal endby the lateral edge 192 of the distal end surface 112. As with themedial side surface 116, the lateral side surface 120 may, in someembodiments, include a lattice-like or web-like outer structure 220 thatis porous and rough. In other embodiments, the entire lateral sidesurface 120 may be smooth and solid.

The lateral side surface 120 defines a lateral side maximum length 224spanning from the furthest proximal portion of the lateral edge 152 ofthe proximal end surface 108 to the furthest distal portion of thelateral edge 192 of the distal end surface 112. The lateral side maximumlength 224 may be, for example, between approximately 3 cm andapproximately 5 cm. In one particular embodiment, the lateral sidemaximum length 224 may be approximately 2 cm shorter than the lateralside length of an average adult human midfoot, or approximately 4 cm, toallow the midfoot implant 100 to be used in a variety of patients.

Additionally, as best seen in FIG. 7 , the lateral side maximum length224 is less than the largest widths 154, 194 of both the proximal anddistal end surfaces 108, 112, but is greater than medial side maximumlength 204. Both the lateral and medial side maximum lengths 204, 224are greater than the largest heights 156, 196 of the proximal and distalend surfaces 108, 112. The reader should appreciate, however, that inother embodiments, the relative dimensions may be different depending onthe particular features and functions of the specific midfoot implant.

With continuing reference to FIG. 7 , the upper or superior surface 124of the midfoot implant 100 is defined on its proximal end by the convexsuperior edge 140 of the proximal end surface 108, and on its distal endby the convex superior edge 180 of the distal end surface 112.Accordingly, the superior surface 124 has a generally convex shapeextending laterally across the midfoot implant 100 from the medial side,at which the superior surface 124 transitions smoothly into the medialside surface 116, to the lateral side, at which the superior surface 124transitions smoothly to the lateral side surface 120.

In the illustrated embodiment, the superior surface 124 is smooth androunded to accommodate tissue, nerves, muscles, and vascular structuresthat rest on the superior surface 124 of the midfoot implant 100 withoutcausing discomfort damage to the tissue, nerves, or muscles. In someembodiments, one or more flat or convex channels may be defined in thesuperior surface 124 so as to accommodate tissues, nerves, muscles, andvascular structures of the foot.

FIG. 8 illustrates the lower or inferior surface 128, which may also bereferred to as the plantar surface. The inferior surface 128 is definedat its proximal end by the concave inferior edge 144 of the proximal endsurface 108, and at its distal end by the concave inferior edge 184 ofthe distal end surface 112. The inferior surface 128 is thereforegenerally concave-shaped, similar to the typical anatomical shape of theplantar region of the midfoot. The medial side of the inferior surface128 transitions smoothly into the medial side surface 116, while thelateral side of the inferior surface 128 transitions smoothly into thelateral side surface 120. In addition, the inferior surface 128 issmooth and rounded to accommodate tissue, nerves, muscles, and vascularstructures that extend beneath the inferior surface 128 of the midfootimplant 100 without causing patient discomfort or damage to the tissue,nerves, or muscles running underneath the midfoot implant 100.

FIGS. 9 and 10 illustrate the midfoot implant 100 in use. The implant100 is arranged such that the proximal end surface 108 engages thecalcaneus 240 and talus 244 bones of the patient's foot, while thedistal end surface 112 engages at least the first and fourth metatarsals248A, 248D. The distal end surface 112 may also engage one or more ofthe second, third, and fifth metatarsals 248B, 248C, 248E.

A first fixating fastener 260 extends through the medial through-hole160 and is anchored at its proximal end in the patient's talus 244, andat its distal end in the patient's first metatarsal 248A. A secondfixating fastener 264 extends through the lateral through-hole 164 andis anchored at its proximal end in the patient's calcaneus 240, and atits distal end in the patient's fourth metatarsal 248D.

In another preferred embodiment, the midfoot implant 100 furtherincludes a blind hole 266 defined in the lateral outside of the distalend surface 112 or in the distal end region of the lateral side surface120, extending only partially into the midfoot implant 100. A thirdfixating fastener 268 affixes the lateral side of the midfoot implant100 to the fifth metatarsal 248E to provide stability for the fifthmetatarsal 248E. Since the peroneus brevis tendon attached to theproximal end of the fifth metatarsal 248E, stabilizing the fifthmetatarsal 248E by fixing it to the midfoot implant 100 increases thestability of the patient, thereby improving the patient's ability towalk after implantation of the midfoot implant 100. Accordingly, theembodiment of the midfoot implant 100 that includes the blind hole 266is particularly effective in improving the patient's mobility.

Additionally or alternatively, the implant may be attached via fourthand/or fifth fixating fasteners 272, 276, which are anchoredrespectively in the second and third metatarsals 248B and 248C. Thefourth and fifth fixating fasteners 272, 276 may extend throughthrough-holes defined in the midfoot implant 100 into the calcaneus 240.Particularly, the fourth and/or fifth fixating fasteners 272, 276 may beused if the first or fourth metatarsals 248A, D are degraded and cannotsupport the respective first and second fixing fasteners 260, 264. Inother embodiments, any combination of the first, second, third, fourth,and/or fifth fasteners 260, 264, 268, 272, 276 may be used.

The fixating fasteners 260-276 may be any desired fasteners, for examplesolid or cannulated screws, nails, pins, rails, or other surgicalfixation devices. Additionally, the third fixating fastener 268 may beshorter than the first and second fixating fasteners 260, 264 since thethird fixating fastener 268 does not extend through the entire midfootimplant 100.

FIG. 11 depicts a process 400 of surgically implanting a midfoot implantsuch as the midfoot implant 100 described above. The process 400 beginswith removing of the cuneiform, navicular, and cuboid bones from thepatient's foot (block 404). In some particular embodiments, thecuneiform, navicular, and cuboid bones are removed in their entirety.

The process 400 continues with inserting the midfoot implant 100. Moreparticularly, the midfoot implant 100 is inserted so that the proximalend surface 108 engages the calcaneus 240 and talus 244, while thedistal end surface 112 engages at least the first and fourth metatarsals248A, 248D. Additionally, the surgeon may reposition at least some ofthe patient's metatarsals 248A-E against the distal end surface 112 insuch a way that the patient's overall foot length may be shortened. Inparticular, in embodiments in which the medial and lateral side maximumlengths 204, 224 are shorter than the average midfoot length, themidfoot implant 100 is usable in a wide variety of patients becauselittle or no harm is caused to the patient by reducing the overalllength of the patient's foot.

The process 400 proceeds with fixating the midfoot implant 100 to thebones of the patient's foot. In one embodiment, the fixation includesinserting the first fixating fastener 260 through the first metatarsal248A and the medial through-hole 160, and into the talus 244 of thepatient. The fixation further includes inserting the second fixatingfastener 264 through the fourth metatarsal 248D and the lateralthrough-hole 264, and into the calcaneus 240. The process 400 mayfurther include inserting the third fixating fastener into the blindhole 266 and the fifth metatarsal 248E so as to stabilize the fifthmetatarsal 248E.

The midfoot implant is designed to be used with a variety of differentpatient foot sizes and shapes. Thus, while the through-holes 160, 164are arranged so as to generally align with the first and fourthmetatarsals 248A, 248D, the surgeon may, if necessary, reposition thepatient's metatarsals 248A, 248D so that the fasteners align with andcan pass through the through-holes 160, 164. The slight alignmentadjustment of the patient's metatarsals 248A, 248D causes little or noharm to the patient, and enables the midfoot implant 100 to be usable ina wide variety of patients without the need for custom placement of thethrough-holes 160, 164.

In the illustrated embodiment, the fixating fasteners 260, 264 areinserted through the first and fourth metatarsals 248A, 248D because thefirst and fourth metatarsals 248A, 248D are typically aligned with thetalus and calcaneus, respectively, and therefore provide a strongconnection between the talus 244 and the first metatarsal 248A, andbetween the calcaneus 240 and the fourth metatarsal 248D. Additionally,as discussed above, it is often desirable for the third fixatingfastener 268 to connect the fifth metatarsal 248E to the midfoot implant100 to stabilize the fifth metatarsal 248E and mitigate any potentialdamage to the peroneus brevis tendon, which connects to the proximal endof the fifth metatarsal 248E on the lateral side thereof. Optionally,however, the fixation may further include inserting the fourth and/orfifth fixating fasteners 272, 276 through the respective second and/orthird metatarsal 248B, 248C and into or through respective holes definedin the midfoot implant 100. In particular, in some embodiments, when thefirst and fourth metatarsals 248A, 248D are degraded or misaligned, thesurgeon may choose to instead or additionally insert the fourth and/orfifth fixing fasteners 272, 276 through the respective second and/ormetatarsal 248B, 248C, and into the talus 244 or calcaneus 248.

The fixating fasteners 260-276 may be inserted by any desired knownsurgical procedure such as, for example, beaming or intramedullarynailing. Once the midfoot implant 100 is fixated to the bones of thepatient's foot, the process 400 is complete.

The disclosed midfoot implant 100 replaces the midfoot bones,particularly the cuneiform, navicular, and cuboid bones, in totality ornear totality. As a result, the diseased and damaged bones affected bythe Charcot foot disease do not remain in the foot. Accordingly, themidfoot implant 100 ensures that the metatarsals are connected tocalcaneus and talus with a solid structure that is not at risk ofdegradation. The likelihood of the patient requiring additionalsurgeries for the midfoot region, which can increase costs and increasethe risk of complications and undesirable patient outcomes, is thusreduced.

Additionally, since the midfoot implant 100 is a solid body 104 formedof a rigid material, the midfoot implant 100 provides improved strengthin the patient's foot, reducing the likelihood of subsequent footinjuries in the midfoot region of the patient's foot. Moreover, theimproved strength of the midfoot implant 100, in addition to the removalof the potentially damaged bones, allows for a reduction in the recoverytime of a patient as compared to a surgery in which some or all of thedamaged bones remain in the patient's foot. The patient can thereforeengage in physical activities sooner, which improves the patient'soverall health. Moreover, the patient is at a lower risk of potentialtrauma caused by subsequent degradation of the patient's foot to theextent that the patient loses stability and experiences a fall.

Finally, because the midfoot bones are removed in totality or neartotality and stabilized by the midfoot implant 100, the risk of furtherdamage to the midfoot bones and the adjacent bones is reduced. As aresult, the likelihood of the foot becoming irreparably damaged isreduced, thereby reducing the likelihood that the patient's foot willrequire amputation.

The midfoot implant 100 may be packaged in a kit to facilitate surgicalimplantation in a patient. FIG. 12 illustrates one such kit 500 forrepairing damaged midfoot bones in a patient. The kit 500 includes themidfoot implant 100 and the first and second fixating fasteners 260,264. In a particular embodiment, the kit 500 further includes the thirdfixation fixating fastener 268, which is shorter than the first andsecond fixating fasteners 260, 264 so as to fixate the fifth metatarsal248E into the blind hole 266. In still other embodiments, the kit 500may include one or both of the fourth and fifth fixating fasteners 272,276.

In some further embodiments, the kit 500 includes at least oneadditional midfoot implant 100A, which is similar to the midfoot implantbut is sized differently. For example, the additional midfoot implant100A may have a length in the proximate-distal direction ofapproximately 1 cm to approximately 3 cm longer than or shorter than themidfoot implant 100, and/or the additional midfoot implant 100A may havea width in the lateral direction of approximately 0.5 to approximately 2cm greater than or less than the midfoot implant 100.

In another embodiment, the kit 500 may include an embodiment of theimplant having two implant pieces, a first piece having a design ofimplant 100 or implant 100A, and a second implant piece in the form of aspacer 504. The spacer 504 includes two end surfaces 508, 512, each ofwhich has a profile that generally aligns with either the proximal endsurface 108 or the distal end surface 112. In another embodiment, one ofthe end surfaces 508, 512 is larger than the other, and may be larger orsmaller than the associated proximal or distal end surface 108, 112. Thetwo end surfaces 508, 512 are spaced apart from one another by a spacerthickness 516. The spacer thickness 516 may be, for example, betweenapproximately 0.5 cm and approximately 2 cm. The spacer 504 also definesthrough-holes 520, 524, which are configured to align with thethrough-holes 160, 164 of the midfoot implant 100 so that the fixationfasteners 260, 264 can extend through the spacers 504. In a secondembodiment, the spacer 504 may also include another through-hole (notshown) that aligns with the blind hole 266 to allow the third fixatingfastener 268 to pass through the spacer 504. The spacer 504 enables thekit 500 to increase the length from the calcaneus and talus to themetatarsals to accommodate feet of various different sizes. In stillother embodiments, the implant of the kit may include more than onespacer.

It will be appreciated that variants of the above-described and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems, applications or methods.Various presently unforeseen or unanticipated alternatives,modifications, variations or improvements may be subsequently made bythose skilled in the art that are also intended to be encompassed by theforegoing disclosure.

1. A method of implanting a midfoot replacement in an adult human footcomprising: removing at least a portion of at least one midfoot bonefrom the adult human foot; and inserting a midfoot replacement into theadult human foot such that a proximal side of the midfoot replacementengages at least one of a calcaneus and a talus of the adult human foot,and a distal side of the midfoot replacement engages at least one of afirst metatarsal and a fourth metatarsal of the adult human foot; andinserting a first fixating fastener through the midfoot replacement fromthe proximal side to the distal side, and affixing the first fixatingfastener in the talus and the first metatarsal.
 2. The method of claim1, further comprising: inserting a second fixating fastener through themidfoot replacement from the proximal side to the distal side, andaffixing the second fixating fastener in the calcaneus and the fourthmetatarsal.
 3. The method of claim 1, further comprising: inserting asecond fixating fastener through the midfoot replacement from theproximal side to the distal side, and affixing the second fixatingfastener in the calcaneus and a metatarsal other than that the firstmetatarsal.
 4. The method of claim 1, wherein removing at least aportion of the at least one midfoot bone comprises removing at least aportion of the navicular and cuneiform bones from the adult human foot.5. The method of claim 4, wherein removing the at least one midfoot bonefurther comprises removing at least a portion of the cuboid bone.
 6. Themethod of claim 5, further comprising: inserting a second fixatingfastener through a second opening through the midfoot replacement fromthe proximal side to the distal side, and affixing the second fixatingfastener in the calcaneus and a metatarsal other than that the firstmetatarsal.
 7. The method of claim 1, wherein the proximal side of themidfoot replacement engages the calcaneus and the talus of the adulthuman foot, and the distal side of the midfoot replacement engages thefirst metatarsal and the fourth metatarsal of the adult human foot. 8.The method of claim 7, wherein the midfoot replacement is formed from asolid block of material, and wherein a proximal surface of the midfootreplacement engages the calcaneus and the talus of the adult human foot,and a distal surface of the midfoot replacement engages the firstmetatarsal and an additional metatarsal of the adult human foot.
 9. Themethod of claim 8, further comprising: inserting a second fixatingfastener through the midfoot replacement from the proximal side to thedistal side, and affixing the second fixating fastener in the calcaneusand a metatarsal other than that the first metatarsal.
 10. The method ofclaim 1, wherein the midfoot replacement is configured to support adulthuman weight in physical activities when engaging the talus and thecalcaneus.
 11. A method of implanting a midfoot replacement in an adulthuman foot comprising: removing at least a majority portion ofnavicular, cuneiform, and cuboid bones from the adult human foot; andinserting a midfoot replacement into the adult human foot such that aproximal side of the midfoot replacement engages a calcaneus and a talusof the adult human foot, and a distal side of the midfoot replacementengages a first metatarsal and at least one other metatarsal of theadult human foot.
 12. The method of claim 11, further comprising:inserting a first fixating fastener through a first opening through themidfoot replacement from the proximal side to the distal side, andaffixing the first fixating fastener in the talus and the firstmetatarsal.
 13. The method of claim 12, further comprising: inserting asecond fixating fastener through a second opening through the midfootreplacement from the proximal side to the distal side, and affixing thesecond fixating fastener in the calcaneus and the fourth metatarsal. 14.The method of claim 12, further comprising: inserting a second fixatingfastener through the midfoot replacement from the proximal side to thedistal side, and affixing the second fixating fastener in the calcaneusand an additional metatarsal other than that the first metatarsal. 15.The method of claim 14, further comprising: inserting a third fixatingfastener through the midfoot replacement from the proximal side to thedistal side, and affixing the third fixating fastener to a metatarsalother than the first metatarsal and the additional metatarsal.
 16. Themethod of claim 14, further comprising: inserting a third fixatingfastener into a hole extending partially into the midfoot replacementfrom the distal side, and affixing the third fixating fastener to ametatarsal other than the first metatarsal and the additionalmetatarsal.
 17. The method of claim 14, further comprising:repositioning at least one of the first metatarsal and the additionalmetatarsal to align the at least one of the first metatarsal and theadditional metatarsal with a respective at least one of the firstfixating fastener and the second fixating fastener.
 18. The method ofclaim 14, wherein the midfoot replacement is formed from a solid blockof material, and wherein a proximal surface of the midfoot replacementengages the calcaneus and the talus of the adult human foot, and adistal surface of the midfoot replacement engages the first metatarsaland an additional metatarsal of the adult human foot.
 19. The method ofclaim 14, wherein inserting the first fixating fastener using beaming.20. The method of claim 11, wherein the midfoot replacement isconfigured to support adult human weight in physical activities whenengaging the talus and the calcaneus.